Direct Observations of Emulsion Flow in Elastohydrodynamically Lubricated Contacts

2006 ◽  
Vol 128 (3) ◽  
pp. 619-623 ◽  
Author(s):  
Haixia Yang ◽  
Steven R. Schmid ◽  
Ronald A. Reich ◽  
Thomas J. Kasun
Keyword(s):  
High Speed ◽  
Direct Method ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Video Camera ◽  
Low Speed ◽  
Digital Video Camera ◽  
Wide Range ◽  
Emulsion Flow ◽  
Side Flow

The lubrication mechanisms with oil-in-water emulsions have been extensively investigated based on the measurements of film thickness and/or tractions in the past few decades. However, direct observation of the emulsion flow, as a more direct method of evaluating suggested explanations, has been greatly restricted by the available instruments, especially the cameras used in collaboration with high-speed bearing simulators. In this paper, a newly devised digital video camera and a microscope were used to directly observe the emulsion flow in an elastohydrodynamic lubrication (EHL) inlet region at a wide range of speeds (0.012m∕s up to 1.5m∕s). Both EHL line and point contacts were considered. Previous observations of low speed oil droplet “stay,” “reverse,” and “penetration” behavior for low-speed line contact were confirmed and extended into high-speed line and point cases, and the results were compared with point contact where significant side flow was observed. Three tight emulsions with different mean droplet sizes were examined on an EHL rig to clarify the droplet behavior and investigate the effect of droplet size on entrainment.

Direct Observations of Emulsion Flow in EHL Contacts

2005 ◽  
Author(s):  
Haixia Yang ◽  
Steven R. Schmid ◽  
Ronald A. Reich ◽  
Thomas J. Kasum
Keyword(s):  
High Speed ◽  
Direct Method ◽  
Flow Behavior ◽  
Point Contact ◽  
Video Camera ◽  
Digital Video Camera ◽  
Droplet Behavior ◽  
Droplet Sizes ◽  
Emulsion Flow ◽  
Side Flow

Oil-in-water emulsions are widely used as lubricants in metal forming, machining and some machinery elements where non-flammable lubricants are required. Their lubricating mechanisms have been extensively investigated based on the measurements of film thickness and/or traction in the past few decades and a number of physical explanations for their performance have been forwarded. However, direct observation of the emulsion flow, as a direct method of evaluating suggested theoretical explanations, has been greatly restricted by the available instruments. In this paper, a newly devised digital video camera and microscope were used to directly observe the emulsion flow in EHL contacts at industrially relevant speeds for both line and point contacts. Previous low-speed results for line contact were confirmed and extended into high-speed cases. That is, some droplets were rejected from the inlet, others penetrated to the contact zone, and others remained fixed in position a certain distance from the edge of contact. For point contact, side flow behavior was also observed, and the number of droplets that remained stationary were limited to a single streamline. To clarify the oil droplet behavior and investigate the effect of particle size on entrainment, three tight emulsions with different mean droplet sizes were examined on an EHD rig at speeds from 12 mm/s up to 1.5 m/s.

Effect of Hydrated Salt Additives on Film Boiling Behavior at Vapor Film Collapse

2008 ◽  
Author(s):  
Takahiro Arai ◽  
Masahiro Furuya
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Film Boiling ◽  
Vapor Film ◽  
Quenching Temperature ◽  
Steel Sphere ◽  
Digital Video Camera ◽  
Collapse Temperature ◽  
Test Film ◽  
Film Collapse

A high-temperature stainless-steel sphere was immersed into various salt solutions to test film boiling behavior at vapor film collapse. The film boiling behavior around the sphere was observed with a high-speed digital-video camera. Because salt additives enhanced condensation heat transfer, the observed vapor film was thinner. Surface temperature of the sphere was measured. Salt additives increased the quenching (vapor film collapse) temperature, because frequency of direct contact between sphere surface and coolant increased. Quenching temperature rises with increased salt concentration. The quenching temperature, however, approaches a constant value when the slat concentration is close to its saturation concentration. The quenching temperature is well correlated with ion molar concentration, which is a number density of ions, regardless of the type of hydrated salts.

Experimental Investigation of Droplet Dynamics on Solid Surfaces: Spreading and Recoil Effects

2006 ◽  
Author(s):  
Kalpak P. Gatne ◽  
Milind A. Jog ◽  
Raj M. Manglik
Keyword(s):  
Surface Tension ◽  
High Speed ◽  
Lower Surface ◽  
Video Camera ◽  
Temporal Variations ◽  
Liquid Viscosity ◽  
Viscous Effects ◽  
Droplet Dynamics ◽  
Digital Video Camera ◽  
The Impact

A study of the normal impact of liquid droplets on a dry horizontal substrate is presented in this paper. The impact dynamics, spreading and recoil behavior are captured using a high-speed digital video camera at 2000 frames per second. A digital image processing software was used to determine the drop spread and height of the liquid on the surface from each frame. To ascertain the effects of liquid viscosity and surface tension, experiments were conducted with four liquids (water, ethanol, propylene glycol and glycerin) that have vastly different fluid properties. Three different Weber numbers (20, 40, and 80) were considered by altering the height from which the drop is released. The high-speed photographs of impact, spreading and recoil are shown and the temporal variations of dimensionless drop spread and height are provided in the paper. The results show that changes in liquid viscosity and surface tension significantly affect the spreading and recoil behavior. For a fixed Weber number, lower surface tension promotes greater spreading and higher viscosity dampens spreading and recoil. Using a simple scale analysis of energy balance, it was found that the maximum spread factor varies as Re1/5 when liquid viscosity is high and viscous effects govern the spreading behavior.

Analysis of Thermal Effect on Elastohydrodynamic Lubrication in Angular Contact Ball Bearing

2015 ◽  
Vol 741 ◽  
pp. 443-448
Author(s):  
Bao Ming Wang ◽  
Xia Lun Yun ◽  
Xing Yao Liao ◽  
Xue Song Mei
Keyword(s):  
Temperature Rise ◽  
High Speed ◽  
Ball Bearing ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Oil Viscosity ◽  
Angular Contact Ball Bearing ◽  
Scanning Method ◽  
Lubrication Performance ◽  
Thermal Ehl

Based on the theory of point contact thermal elastohydrodynamic lubrication (EHL),the mathematical models for the thermal EHL of high-speed angular contact ball bearing are established. Multi-grid method and multigrid integration method are respectively used to calculate out the film pressure and film thickness respectively,and the column-by-column scanning method is used to calculate temperature rise of isothermal EHL and thermal EHL. The calculation results show that, under the pure rolling condition, temperature rise of oil film temperature is mainly caused by the compression work and shear heat at inlet and the heat in contact zone mainly comes from the inlet and the heat conduction around; the temperature rise results in oil viscosity lower and the lubricating film thinner ,in this way it reduces the lubrication performance in contact pair.

In-Flow Oscillation of Circular Cylinders in Cross-Flow

2007 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Hiroshi Haruguchi ◽  
Hiroyuki Nakajima ◽  
Toyohiro Sawada ◽  
Kozo Sugiyama
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Vortex Motion ◽  
Cross Flow ◽  
Video Camera ◽  
Circular Cylinders ◽  
Flow Oscillation ◽  
Single Cylinder ◽  
Digital Video Camera ◽  
Flow Oscillations

The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using totally nine cylinders in a water tunnel. Six cases, one single cylinder, two & three cylinders in parallel & in tandem, and a nine cylinder bundle, are examined. Every cylinder can move only in in-flow direction. The motion of cylinders is measured by the strain gages and by a high-speed digital video camera. The results are compared with the visualized vortex motion.

Bubble Lift-Off Diameter in Forced Convective Boiling Flow

2010 ◽  
Author(s):  
In-Cheol Chu ◽  
Chul-Hwa Song
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Bubble Nucleation ◽  
Present Observation ◽  
Convective Boiling ◽  
Digital Video Camera ◽  
Nucleation Frequency ◽  
Boiling Flow ◽  
Lift Off ◽  
Basic Features

A series of experiments were carried out to investigate the bubble nucleation to lift-off phenomena for a subcooled boiling flow in a vertical annulus channel. A high speed digital video camera was used to capture the dynamics of the bubble nucleation to lift-off process. A total of 148 recordings were made, and the bubble lift-off diameter and the bubble nucleation frequency were evaluated for 118 recordings up to now. The basic features of the lift-off diameter and nucleation frequency were addressed based on the present observation. A database for the bubble lift-off diameter was built by gathering and summarizing the data of Prodanovic et al., Situ et al., and the present work. The prediction capability of Unal’s model, Situ et al.’s model, and Prodanovic et al.’s correlation was evaluated against the database. The best prediction results were obtained by modifying the wall superheat correlation in Unal’s model.

Bending Hysteresis Losses in Cord—Rubber Composites

1974 ◽  
Vol 47 (2) ◽  
pp. 376-383
Author(s):  
John Skelton
Keyword(s):  
Direct Measurement ◽  
Experimental Technique ◽  
High Speed ◽  
Cyclic Strain ◽  
Current Version ◽  
Rubber Composites ◽  
Low Speed ◽  
Hysteresis Losses ◽  
Wide Range ◽  
Hostile Environments

Abstract An experimental technique is described which permits the direct measurement of the bending hysteresis loss in cord—rubber composites under carefully controlled conditions of cyclic strain. The equipment can readily detect differences between composites made with different cords. The current version of the equipment is intended only for low-speed cycling, but the extension to high speed capability is contemplated. The robust nature of equipment should make it possible to carry out tests in a wide range of hostile environments.

Lubricating Grease Replenishment in an Elastohydrodynamic Point Contact

1993 ◽  
Vol 115 (3) ◽  
pp. 501-506 ◽  
Author(s):  
Henrik A˚stro¨m ◽  
Jan Ove O¨stensen ◽  
Erik Ho¨glund
Keyword(s):  
Film Thickness ◽  
High Speed ◽  
Video Recording ◽  
Point Contact ◽  
Video Camera ◽  
Lubricating Oil ◽  
Spin Motion ◽  
Lubricating Grease ◽  
Lubricating Film ◽  
Theoretical Predictions

A ball and disk apparatus was used to investigate the lubricant replenishment of an elastohydrodynamically lubricated point contact. This replenishment of the contact is crucial for building up a lubricating film. Whereas lubricating oil manages to achieve replenishment, lubricating grease appears not to achieve this, with lubricant starvation and a dramatic decrease in film thickness as a result. The distribution of grease around the contact was studied using normal and high-speed video. The movements of grease in the vicinity of the contact could be seen by adding molybdenum disulfide particles to the grease. A recording was then made, using highspeed video recording. The overall cavitation regions were studied using an ordinary video camera and grease without particles. On the basis of the results, possible lubricating grease replenishment mechanisms are discussed. The resulting film thickness was also compared with theoretical predictions using the Hamrock and Dowson starvation criterion, assuming negligible replenishment. The measured film thickness was larger than the predicted, which indicated that some replenishment occurs. In the case of an ordinary thrust ball bearing, replenishment was found to rely on the spin motion of the balls.

An experimental study of transverse ionizing MHD shock waves

1968 ◽  
Vol 2 (4) ◽  
pp. 633-652 ◽  
Author(s):  
Charlles F. Stebbins ◽  
George C. Vlases
Keyword(s):  
Magnetic Field ◽  
Shock Waves ◽  
High Speed ◽  
Initial Conditions ◽  
Easy Access ◽  
Low Speed ◽  
Wide Range ◽  
Image Position ◽  
Shock Jump Relations ◽  
The Magnetic Field

The jump conditions across a transverse ionizing MHD shock wave, where the magnetic field is in the plane of the shock, are examined. The conservation laws, in conjunction with Maxwell's laws and the equation of state, yield three jump equations in four unknowns. To uniquely describe jumps across an ionizing wave requires an additional descriptive relationship. The theory of Kulikovskii & Lyubimov and, later, Chu, in which the internal structure of the shock itself supplies the missing relationship, is examined. In particular, Kulikovskii & Lyubimov show, for appropriate ratios of thermal to magnetic diffusivities, that for low-speed waves the magnetic field compression across the shock is unity and the jump equations reduce to the ordinary Rankine—Hugoniot relations. For high-speed shock waves, the magnetic field compression, B2/B1, equals the gas compression across the wave, p2/p1, and the jump equations become the magnetohydrodynamic shock jump relations. Furthermore, intermediate speed shocks induce magnetic field compressions between 1 and p2/p1. An experiment was performed in an inverse pinch where E behind the shock, the shock and piston velocities, and the magnetic field compression across the shock, were measured over a wide range of initial conditions and shock velocities in hydrogen. The jump relations were written with B2/B1 as a parameter and programmed into a digital computer. The program was written for real, equilibrium hydrogen. The program provided easy access to a unique solution of the jump equations for any B2/B1. The experiment tends to confirm the Kulikovskii—Lyubimov—Chu theory. Ordinary shock waves were observed at low speeds and near-MilD shocks were observed at high speeds. Further, the relation was verified for the plasma behind the shock for low-speed shock waves, and was verified to within experimental accuracy for the intermediate class of shock waves.

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